Preliminary Technical Data
UG-1828
Rev. PrC | Page 205 of 338
Figure 191. ADRV9001 DPD Model 4 LUT Configuration
As shown in Figure 191, d(t) is the raw complex transmit signal before predistortion. Its amplitude is the basis that the DPD actuator uses
to predistort the d(t) via its L UT. The LUT consists of four taps, which are calculated with precomputed DPD coefficients α, as the
following:
TAP
0
=
a
0,0,0
+
a
0,0,1
|
d
(
t
)| +
a
0,0,2
|
d
(
t
)|
2
+
a
0,0,3
|
d
(
t
)|
3
+
a
0,0,4
|
d
(
t
)|
4
TAP
1
=
a
1,1,0
+
a
1,1,1
|
d
(
t −
1)| +
a
1,1,2
|
d
(
t −
1)|
2
+
a
1,1,3
|
d
(
t −
1)|
3
+
a
1,1,4
|
d
(
t −
1)|
4
+ a
1,1,5
|
d
(
t –
1
)|
5
+ a
1,1,6
|d(t –
1
)|
6
TAP
2
=
a
2,2,0
+
a
2,2,1
|
d
(
t −
2)| +
a
2,2,2
|
d
(
t −
2)|
2
+
a
2,2,3
|
d
(
t −
2)|
3
+
a
2,2,4
|
d
(
t −
2)|
4
TAP
3
=
a
3,2,1
|
d
(
t −
2)| +
a
3,2,2
|
d
(
t −
2)|
2
+
a
3,2,3
|
d
(
t −
2)|
3
+
a
3,2,4
|
d
(
t −
2)|
4
Note the TAPx equations represent the default power term setting for each tap in Model 4, from which,
𝑏𝑏
𝑡𝑡
,
𝑙𝑙
𝑡𝑡
,
𝑖𝑖
can be easily derived as the
following depending if a power term is included or excluded:
Tap 0:
b
0,0,0
= 1,
b
0,0,1
= 1,
b
0,0,2
= 1,
b
0,0,3
= 1,
b
0,0,4
= 1,
b
0,0,5
= 0,
b
0,0,6
= 0,
b
0,0,7
= 0
Tap 1:
b
1,1,0
= 1,
b
1,1,1
= 1,
b
1,1,2
= 1,
b
1,1,3
= 1,
b
1,1,4
= 1,
b
1,1,5
= 1,
b
1,1,6
= 1,
b
1,1,7
= 0
Tap 2:
b
2,2,0
= 1,
b
2,2,1
= 1,
b
2,2,2
= 1,
b
2,2,3
= 1,
b
2,2,4
= 1,
b
2,2,5
= 0,
b
2,2,6
= 0,
b
2,2,7
= 0
Tap 3:
b
3,2,0
= 0,
b
3,2,1
= 1,
b
3,2,2
= 1,
b
3,2,3
= 1,
b
3,2,4
= 1,
b
3,2,5
= 0,
b
3,2,6
= 0,
b
3,2,7
= 0
If using an array B for 4 taps and for each tap using a byte to represent the above setting (the least significant bit represents the 0th power
term), it is clear that the default setting is equivalent to B[0] = 0x1F, B[1] = 0x7F, B[2] = 0x1F and B[3] = 0x1E.
The connections from the 4 outputs are combined to produce the final output, x(t) as the following:
x(t)
=
TAP
0
[|
d
(
t
)|] ×
d
(
t
) + {
TAP
1
[|
d
(
t
− 1)|] +
TAP
3
[|
d
(
t
− 2)|]} ×
d
(
t
– 1) +
TAP
2
[|
d
(
t
− 2)|] ×
d
(
t
– 2)
changeModelTapOrders
This flag is used to provide user an option to select the default model tap orders or choose a customized model tap orders. If this flag is set
to be “TRUE”, the next field in the data structure “modelOrdersForEachTap”, should be used to set the model tap orders for the specified
channel. If it is “FALSE”, then “modelOrdersForEachTap” will be ignored and it will use the default tap orders as discussed (B[0] = 0x1F,
B[1] = 0x7F, B[2] = 0x1F and B[3] = 0x1E).
modelOrdersForEachTap
This is an array of bitmaps
𝑏𝑏
𝑡𝑡
,
𝑙𝑙
𝑡𝑡
,
𝑖𝑖
(
𝑖𝑖
= 0
𝑎𝑎𝑡𝑡
7)
for each tap t (t=0 to 3), formulated in the same way as discussed above for the default
setting. It provides user an option to customize the order so that a power term could be included or excluded in the polynomial to better
model the PA. Table 83 shows recommendations for setting this field. The user could try those suggestions and find out the best model
through tests. The method of selecting the best model tap orders is discussed in the DPD Tuning and Testing section as a part of DPD
tuning recommendations.
Table 83. Suggested Model Orders for Narrow-Band Waveforms
Taps
Model Orders for Each Tap
Tap 1
B[1] = 0x1F, 0x3F, 0x7F, 0xFF
Tap 0 and Tap 2
B[0] = B[2] = 0x03, 0x07, 0x0F, 0x1F, (Tap 0 and Tap 2 should be the same.)
Tap 3
B[3] = 0x0, 0x02, 0x06, 0x0E, 0x1E, 0x3E
The user could configure the changeModelTapOrders and modelOrdersForEachTap through TES, as shown in Figure 192 and Figure 193 .
Figure 192 shows the default model tap configuration and Figure 193 shows a customized model tap configuration which is equivalent to
x
x
+
+
Z
1
TAP
1
TAP
3
TAP
2
TAP
0
Z
1
Z
1
x
Z
1
Z
1
Z
1
Z
1
LUT
0
1
3
2
d(
t
)
d
(t)
d
(t
– 1
)
d
(t
– 2
)
x
(t)
|d(
t
)|
24159-
149
